Fuse plug



Dec. 29, 1925. Y 1,567,529

- H. w. MCQUAID FUSE PLUG Filed April 17, 1922 59am 37a v 6cm u [iv/walla,

Patented Dec. 29, 1925.

UNITED STATES PATENT OFFICE HARRY W. MCQUAID, OF CANTON, OHIO, ASSIGNOR OF FIFTY-TWO HUNDREDTHS TO AARON L. LEWIS AND TWENTY-FOUR HUNDREDTHS TO CHARLES E. RUNYON,

BOTH OF CANTON, OHIO.

FUSE FLUG.

Application filed April 17, 1922.

To all whom it may concern:

Be it known that I, HARRY W. MGQUAID, a citizen of the United States, residing at Canton, in the county of Stark and State i of Ohio, have invented a new and useful Fuse Plug, of which the following is a specification.

This invention relates to fuse plugs for electrical circuits and more particularly to 1 a fuse plug provided with means for indicating the condition of the fuse at all times so as to ascertain readily whether or not the fuse has been blown.

With the usual type of fuse plug at pres- .15 out in general use, no means is provided for indicating which one of a number of fuses has blown, and considerable time and trouble is often necessitated in examining and testing the several fuses before the defective one can be located.

The objects of the present invention are to provide indicating means which may be readily attached to any common type of fuse plug which will indicate at a glance the condition of the fuse.

The above and other objects may be attained by providing a spring arm arranged to be attached within the chamber of the fuse plug and insulated from the circuit, a hook being provided upon the free end of the arm for engagement with the usual fusible link, a target being carried by the arm and arranged to be displayed against the mica cover of the fuse plug when the spring arm is released by the separation of the fusible link.

An embodiment of the invention thus set forth in general terms is illustrated in the accompanying drawing, in which- Figure 1 is a longitudinal sectional view through a fuse plug provided with the indicator embodying the invention, showing the same in the normal position in which it is held during the continuity of the fusible link;

Fig. 2, a top plan view of the same;

Fig. 3, a view similar to Fig. 1, showing the indicating arm released by the separation of the fusible link, the target being held against the transparent cover of the fuse plug;

Fig. 4, a plan view of the same; and

Fig. 5, a detail perspective view of the Serial No. 553,817.

indicating device removed from the fuse plug.

Similar numerals indicate similar parts throughout the drawing.

The fuse plug may be of any common or well known type and comprises the body 1 formed of porcelain or other suitable insulating material having theinterior chamber :2 and the annular flange 3 at its upper end which accommodates the clamping ring 4 by means of which the transparent cover 5 of mica, isinglass or similar material is fixed over the open end of the body 1 by means of which the interior chamber of the fuse plug is visible.

The usual threaded brass shell 6 surrounds the body portion of the plug for engagement with the usual internally threaded fuse receptacle, and one end of the fusible link or wire 7 is connected to said shell as at 8, the other end thereof being connected to the central contact 9 of the plug. This is the usual construction of fuse plug and may be varied without departing from the invention.

l/Vhen the fuse plug is located in the recept-acle provided therefor, the circuit is completed through the fusible link 7 and as is well understood, an excess current passing through the fuse causes a fusion of this link, melting away a portion of the same and breaking the circuit.

As it is generally difficult for a person to see the break or separation in the fusible link or wire, it usually happens that where one of a number of fuse plugs is blown out, considerable time is required to locate the defective fuse.

The present invention contemplates the attachment of an indicator within the interior chamber of the fuse plug, so arranged that it will indicate at a glance the condition of the fuse, obviating the necessity of removing any of the fuse plugs to test the same.

This indicator comprises in its broadest conception a spring arm connected to and insulated from the body of the fuse plug and extending within the interior chamber thereof, the free end of said arm normally engaging the fusible link or Wire, the continuity of which holds the arm in the inoperative position, a target being carried by the arm and arranged to be displayed against the transparent cover of the fuse plug when the arm is released by the separation of the fusible link.

The simplest form of the invention comprises a spring wire 10 arranged to be inserted into a suitable opening 11 located longitudinally through the insulated body of the fuse plug at a point adjacent to the connection 8 of the fusible link or wire 7 with the threaded shell 6.

A coil 12 is formed intermediate the extremities of the wire 10, the free arm 13 being provided at its extremity with a hook 14f arranged to engage the fusible link or wire '7 as shown in Figs. 1 and 2. A target 15, which may be painted white to attract attention, is fixed upon the upper side of the arm 18 near the free extremity thereof.

In the normal position of the device, the hook 1 1 is engaged with the fusible link or wire, holding the arm 13 down as shown in Figs. 1 and 2, the target 15 being held away from the transparent cover 5 of the fuse plug during the continuity of the fusible link or wire.

When the fuse is blown, the fusible link or wire 7 will be separated as shown in Figs. 3 and a, releasing the spring arm 18 from engagement therewith and permitting the same to spring upward into the position shown in Figs. 3 and 4, holding the target 15 in engagement with the transparent cover of the fuse plug where it is readily visible, indicating to the user that the fusible link or wire of the fuse plug has separated.

From the above description and an inspection of the accompanying drawing, it will be evident that a simple and inexpensive attachment is provided which may be easily connected to a fuse plug of usual construction and which will efliciently and au tomatically operate to indicate at a glance the condition of the fuse, without the necessity of removing the fuse plug from its receptacle.

I claim 1. In a fuse plug including a chamber, a fusible link located therein and a transparent cover for the chamber, a spring arm mounted within the chamber and not forming a part of the circuit through the fuse plug, a hook upon the arm for engagement with the fusible link and a target upon the arm arranged to be projected against the transparent cover when the fusible link is parted.

2. In a fuse plug including a chamber, a fusible link located therein and connected at opposite ends to terminals within the chamber, and a transparent cover for the cham her, a spring arm mounted within the chamher and not forming a part of the circuit through the fuse plug, a hook upon the arm for engagement with the fusible link intermediate the terminals and a target upon the arm arranged to be projected against the transparent cover when the fusible link is parted.

An indicating attachment for a fuse plug having a chamber, a fusible link therein and a trans 'iarent cover for the chamber, comprising a spring wire not forming a part of the circuit through the fuse plug and having a coil intermediate its extremities, one end of the wire being arranged to be connected to an insulating portion of the plug, a hook upon the other-end of the wire for engagement with the fusible link and a target adjacent to the hook arranged to be projected against the transparent cover when the fusible link is parted.

a. In a fuse plug having a chamber, a fusible link located diagonally therein and a transparent cover for the chamber, and an indicating attachment comprising an angular spring wire not forming a part of the circuit through the fuse plug and having a coil at the angle, one end of the wire being connected to an insulating portion of the plug adjacent to one end of the fusible link, a hook upon the other end of the wire for engagement with an intermediate portion of the fusible link and a target upon the wire, adjacent to the hook, arranged to be projected against the transparent cover when the fusible link is parted.

HARRY W. MOQUAID. 

